TWI586986B - Magnetic sensor device - Google Patents

Description

Magnetic sensor device

The present invention relates to a magnetic sensor device for converting a magnetic field strength into an electrical signal, for example, a sensor for detecting a switch state used in a foldable mobile phone or a notebook computer, or a sense of rotational position detection of a motor. A magnetic sensor device such as a detector.

A magnetic sensor device is used in the case of a switch state detecting sensor in a folding mobile phone or a notebook computer, or a rotational position detecting sensor of the motor.

The magnetic sensor device outputs a voltage proportional to the magnetic field strength or the magnetic flux density by a magnetoelectric conversion element (for example, a Hall element), amplifies the output voltage of the amplifier, and uses a comparator to determine the H signal or the L signal. The binary output. Since the output voltage of the magnetoelectric conversion element is small, the bias voltage (element bias voltage) held by the magnetoelectric conversion element, or the bias voltage (input bias voltage) held by the amplifier or the comparator, is magnetically sexy. The noise in the detector device becomes a problem. The component bias voltage is mainly generated by the magnetoelectric conversion element being subjected to stress or the like by the package. Input offset The voltage is mainly generated by a characteristic deviation or the like of an element constituting an input circuit of the amplifier. The noise is mainly generated by the scintillation noise, the single crystal or the thermal noise held by the resistive element held by the single crystal of the circuit.

Proposal to reduce the above magnetoelectric conversion element or amplifier holding A magnetic sensor device that affects the bias voltage (see, for example, Patent Document 1). The conventional magnetic sensor device shown in FIG. 4 includes a Hall element 51 belonging to a magnetoelectric conversion element, a switch switching circuit 52, a differential amplifier 53, a comparator 54, a detection voltage setting circuit 55, a first capacitor C51, and a second Capacitor C52, first switch S51 and second switch S52.

The differential amplifier 53 becomes the measuring amplifier structure shown in FIG. The differential amplifiers 61 and 62 and the resistors R61, R62, and R63 are provided. The differential amplifiers 61 and 62 operate as non-inverting amplifiers, respectively. The first input terminal of the differential amplifier 53 is connected to the non-inverting input terminal E61 of the differential amplifier 61, the second input terminal is connected to the non-inverting input terminal E62 of the differential amplifier 62, and the first output terminal is connected to The output terminal E63 of the differential amplifier 61 and the second output terminal are connected to the output terminal E64 of the differential amplifier 62. The differential amplifier 53 is capable of suppressing the influence of the in-phase noise in the differential input by providing such a measurement amplifier. Here, the amplification factors of the differential amplifiers 61 and 62 are set to be equal.

Figure 6 shows the operation of the conventional magnetic sensor device Sequence diagram. The one period T of the detecting operation is divided into the first terminal pair A-C input power supply voltage of the Hall element 51 and the first detection of the detection voltage from the second terminal pair B-D by the action of the above-described switch switching circuit 52. State T1, and a supply voltage to the second terminal pair B-D, and a second detection state T2 of the detection voltage is output from the first terminal pair A-C. Furthermore, the switches are divided into a first sampling phase F1, a second sampling phase F2, and a comparison phase F3. Then, each offset component is removed in the comparison phase F3.

[Advanced technical literature]

[Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2010-281801

However, in the conventional magnetic sensor device, in order to offset the offset component, such as the sample phase and the comparison phase, it is necessary to have a time division operation during which the signal processing period is set, which is not suitable for high-speed signal processing. Furthermore, in order to perform the time division operation, it is necessary to have a connection of a switching circuit or a capacitance element, and the circuit configuration becomes complicated.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a high precision magnetic field strength detection and high speed signal processing by utilizing a comparator having a plurality of Hall elements and a plurality of differential input pairs to offset the bias component of the Hall element. Magnetic sensor device.

In order to solve the problem of the past, the magnetic sexy of the present invention The detector device is constructed as follows.

A magnetic sensor device comprising: a plurality of Hall elements, a plurality of variable resistors respectively connected to a plurality of Hall elements, and a plurality of differential amplifiers respectively connected to the plurality of Hall elements, respectively having a complex number The comparator of the differential input pair of the differential amplifier is connected.

According to the magnetic sensor device of the present invention, since the detection voltage level of the magnetic field strength can be arbitrarily set in a small-scale circuit, the Hall element offset can be canceled, and the signal processing can be performed at high speed.

1a, 1b, 51‧‧‧Horse components

2a, 2b, 53‧‧‧Differential Amplifier

3, 54‧‧‧ comparator

55‧‧‧Detection voltage setting circuit

52‧‧‧Switching circuit

Ra, Rb‧‧‧Variable Resistors

Fig. 1 is a circuit diagram showing a magnetic sensor device of the present embodiment.

Fig. 2 is a circuit diagram showing a Hall element and a variable resistor of the present embodiment.

Fig. 3 is an example of a circuit diagram of a comparator used in the embodiment.

4 is a circuit diagram of a conventional magnetic sensor device.

Fig. 5 is a circuit diagram showing an example of a differential amplifier of a conventional magnetic sensor device.

Fig. 6 is a timing chart of a conventional magnetic sensor device.

Hereinafter, the embodiment of the present invention will be described with reference to the drawings. One side will explain in detail. The magnetic sensor device of the present invention is used as a sensor for detecting a state of a magnetic field strength as a switch state detecting sensor in a folding mobile phone or a notebook computer, or a rotational position detecting sensor of a motor or the like. Widely used. In the following embodiments, the magnetic sensor device using the Hall element is described. However, the magnetic sensor device of the present invention can perform the same voltage output in response to physical quantities such as acceleration or pressure. The conversion element replaces the Hall element that performs voltage output in response to the strength of the magnetic field.

1 is a view showing a magnetic sensor device related to the present invention A circuit diagram of an embodiment. The magnetic sensor device of the present embodiment is a Hall element 1a, 1b that outputs a signal voltage in response to a magnetic field strength, a differential amplifier 2a, 2b that amplifies a signal voltage, a comparator 3 having two differential input pairs, and The variable resistors Ra and Rb connected to the Hall element are formed.

The Hall elements 1a and 1b are arranged on a semiconductor substrate. In a position that is not close, a straight line connecting the first terminal pair A-C of the Hall element 1a and a line connecting the first terminal pair E-G of the Hall element 1b are arranged in parallel relationship with each other. As a result, the straight line connecting the second terminal pair B-D of the Hall element 1a and the straight line connecting the second terminal pair F-H of the Hall element 1b are also in parallel relationship with each other. The differential amplifiers 2a and 2b have a configuration of a measuring amplifier as shown in FIG. 5 in the description of the conventional example. The details of the comparator 3 will be described later in the circuit configuration shown in FIG. 3, and the voltage VO of the output terminal OUT is expressed by the formula (1).

VO=A1(V6-V5)+A2(V8-V7). . . (1)

Here, A1 and A2 are respective amplification factors of the two differential amplifiers constituting the comparator 3. The variable resistors Ra and Rb are respectively connected between one terminal of the differential amplifier 2a of the hall element 1a and the ground, and between one of the terminals of the differential amplifier 2b of the hall element 1b and the ground.

Next, the operation of the magnetic sensor device of the present embodiment will be described. The differential output voltage of the pair of output terminals of the Hall elements 1a and 1b with respect to the magnetic field component is Vh, the component bias voltage is Voh, and the in-phase voltage is Vcm (≒VDD/2), and the differential is The respective amplification factors of the amplifiers 2a and 2b are G, and the detection voltage components of the output terminal pairs of the Hall elements 1a and 1b determined by the variable resistors Ra and Rb are Vrefa and Vrefb, respectively, for the signal components. The communication is explained. Since the flow direction of the current is rotated by 90 degrees in the Hall elements 1a and 1b, the bias component of the pair of output terminals of the Hall element 1a and the bias component of the pair of output terminals of the Hall element 1b are reversed. Based on the above, when calculating the signal voltage of each connection point, it is as follows.

V1=Vcm-Vh/2+Voh/2. . . (2)

V2=Vcm+Vh/2-Vrefa-Voh/2. . . (3)

V3=Vcm-Vh/2-Voh/2. . . (4)

V4=Vcm+Vh/2-Vrefb+Voh/2. . . (5)

V5=Vcm-G(Vh/2-Voh/2). . . (6)

V6=Vcm+G(Vh/2-Vrefa-Voh/2). . . (7)

V7=Vcm-G(Vh/2+Voh/2). . . (8)

V8=Vcm+G(Vh/2-Vrefb+Voh/2). . . (9)

When the above V5 to V8 are substituted into the equation (1), the voltage VO is expressed by the equation (10). Here, the comparator 3 is different in each differential amplifier. The configuration is generally set to A1=A2=A.

VO=AG(2Vh-Vrefa-Vrefb). . . (10)

As a result, it can be seen that the offset components of the Hall elements 1a and 1b are offset, and the amplified signal component of the magnetic field strength and the arbitrarily set detection voltage component can be compared. In the above calculation, it is assumed that one of the variable resistors is connected to the variable resistor Ra between the terminal B of the hall element 1a and the ground, and the variable resistor Rb between the terminal G of the hall element 1b and the ground. The connection destination is switched from terminal B to terminal D, and the same result is obtained when switching from terminal G to terminal E. At this time, the polarity of the detected magnetic field intensity is reversed. Further, when the connection destination of the other end of the variable resistor is switched from the ground terminal GND to the power supply voltage terminal VDD, the same result is obtained.

In the present embodiment, since the voltage VO is a comparator (the value of A is very large), it is an H signal (VDD potential) or an L signal (GND potential) in response to the value of Vh. Moreover, the series of signal processing does not require time-division signal processing as in the prior art, and high-speed signal processing can be performed. It is also not used for the switching circuit or capacitor element required for time signal processing, which can reduce the size of the wafer, which is also contributing to the cost reduction.

Here, Vrefa or Vrefb of the above-described detected voltage component will be described. As shown in Fig. 2, the Hall elements 1a and 1b are respectively represented by equivalent bridge circuits composed of resistors R1 to R4 and R5 to R8. One end of the variable resistor Ra is connected to the terminal B of the hall element 1a, and the other end is connected to the ground. Similarly, the variable resistor Rb is connected at one end to The terminal G of the Hall element 1b is connected to the ground at the other end. Next, the action will be described. When the potential of the terminal B and the potential of the terminal D are equal in the Hall element 1a, that is, when the potentials of the first differential input pair in the comparator of the subsequent stage are considered to be equal, the equation (11) is established. Relationship.

Ra = R1 × R2 × R3 / (R2 × R4 - R1 × R3). . . . . (11)

Here, in the state where no magnetic field is applied, when R1=R2=R3=R4=R, or a variation amount of each resistance value in a state of a magnetic field of a certain magnitude is ΔR, the above formula (11) In the state, it is conceivable that R1 = R - ΔR, R2 = R + ΔR, R3 = R - ΔR, and R4 = R + ΔR. When this is substituted into the formula (11), the formula (12) is derived.

Ra=R ² (1-ΔR/R-(ΔR/R) ² +(ΔR/R) ³ )/(4△R). . . . . (12)

Since ΔR is much smaller than R, when the second or third term of (ΔR/R) is ignored, the equation (13) is established.

△R/R≒1/(1+4Ra/R). . . . . (13)

Therefore, in the present embodiment, the detection voltage can be determined only by the resistance ratio Ra/R without depending on the power supply voltage or the manufacturing variation. As a result, a highly accurate detection voltage level setting can be achieved. Similarly, even in the Hall element 1b, the detection voltage can be determined by the variable resistor Rb. According to the above, the detected voltage components Vrefa and Vrefb are derived as follows.

Vrefa≒1/(1+4Ra/R) VDD. . . . . (14)

Vrefb≒1/(1+4Rb/R) VDD. . . . . (15)

Furthermore, the comparator 3 will be described. The comparator 3 has a circuit configuration as shown in FIG. 3, and has a constant current circuit I1, NMOS transistors M43, M44A, M44B, M45A, M46A, M45B, M46B, and PMOS transistors M41 and M42, and is connected as follows. . One of the constant current circuits I1 is connected to the power supply voltage terminal VDD, and the other is connected to the drain and the gate of the NMOS transistor M43. Set this connection point to VBN. The VBN is connected to the gates of the NMOS transistors M44A, M44B. The sources of the NMOS transistors M43, M44A, and M44B are connected to the ground terminal VSS. The sources of the NMOS transistors M45A and M46A are connected to the drain of the M44A, and the sources of the NMOS transistors M45B and M46B are connected to the drain of the M44B. The drains of the NMOS transistors M45A and M45B are connected to the drain of the PMOS transistor M41. Set this connection point to VA. The drains of the NMOS transistors M46A and M46B are connected to the drain of the PMOS transistor M42. This connection point is connected to the output terminal OUT of the comparator 3. The gates of the PMOS transistors M41 and M42 are connected to the connection point VA, and the source is connected to the power supply voltage terminal VDD. The gates of the NMOS transistors M45A and M46A are respectively connected to the second input terminal V6 of the first differential input pair, the first input terminal V5, and the gates of the NMOS transistors M45B and M46B are respectively connected to the second differential input. The second input terminal V8 and the first input terminal V7.

Next, the operation of the comparator 3 will be described. The constant current circuit I1 generates a constant current and supplies it to the NMOS transistor M43. NMOS transistor The bodies M43, M44A, and M44B constitute a current mirror circuit, and a current flowing according to a current flowing between the drain and the source of M43 flows between the drain and the source of the NMOS transistors M44A and M44B. The five transistors formed by the NMOS transistors M44A, M45A, M46A, and the PMOS transistors M41 and M42 constitute a differential amplifier, and the difference between the gate voltages of the NMOS transistors M45A and M46A is amplified, that is, the first differential input pair. The voltage difference between the second input terminal V6 and the first input terminal V5 acts to output to the output terminal OUT. This magnification is set to A1. Here, the operation of the configuration of the current mirror circuit and the configuration of the differential amplifier is described in detail in the literature of the CMOS analog circuit, and the detailed description thereof is omitted here. Furthermore, the five transistors composed of the NMOS transistors M44B, M45B, M46B, and the PMOS transistors M41 and M42 constitute a differential amplifier, and the difference between the gate voltages of the NMOS transistors M45B and M46B is a second difference. The voltage input difference between the second input terminal V8 and the first input terminal V7 is input to the output terminal OUT. This magnification is set to A2. Furthermore, the drains of the NMOS transistors M45A and M45B are connected to the drain of the PMOS transistor M41 at the connection point VA, and the drains of the NMOS transistors M46A and M46B are connected to the PMOS transistor M42 at the output terminal OUT. In this case, the connection point VA and the output terminal VO operate as a signal voltage that is input to each differential amplifier and amplified. These actions are expressed by the equation, as in the above formula (1).

Further, in the present embodiment, the Hall element and the variable resistor are respectively increased by, for example, four, and the differential input pair of the comparator is increased to four (8 input terminals), thereby suppressing the Huo Ear element The influence of the offset deviation can also improve the detection accuracy of the magnetic field strength. As such, the present invention can correspond to the construction of a comparator having a plurality of Hall elements and a plurality of differential input pairs.

Furthermore, the magnetic sensor device shown in the embodiment of the present invention can also be configured as an output analog signal by changing the comparator to a differential amplifier.

1a, 1b‧‧‧Horse components

2a, 2b‧‧‧Differential Amplifier

3‧‧‧ comparator

Ra, Rb‧‧‧Variable Resistors

Claims (2)

A magnetic sensor device is a magnetic sensor device that outputs according to a magnetic field strength applied to a Hall element, and is characterized in that: a plurality of Hall elements are provided; and a plurality of variable resistors are respectively connected a plurality of Hall elements; a differential amplifier having a first input terminal and a second input terminal connected to respective output terminals of said plurality of Hall elements; and a comparator having a difference from said complex number The differential input pair of the complex amplifier connected. The magnetic sensor device according to claim 1, wherein the plurality of differential amplifiers are a first differential amplifier and a second differential amplifier, and the first differential amplifier is a first input terminal and a second The input terminal is connected to the output terminal pair of the first Hall element, and outputs the amplified signal voltage to the first output terminal and the second output terminal; the second differential amplifier is a first input terminal and a second input terminal The output terminal pair of the two Hall element is connected, and the amplified signal voltage is output to the first output terminal and the second output terminal, wherein the variable resistor is a first variable resistor and a second variable resistor, and the first variable The resistor is connected between one of the pair of output terminals of the first Hall element and the power terminal or the ground terminal; The second variable resistor is connected between one of the output terminal pairs of the second Hall element and a power supply terminal or a ground terminal; and the comparator includes the following components: a first differential input pair, The first input terminal and the second input terminal are connected to the first output terminal and the second output terminal of the first differential amplifier; and the second differential input pair is a first input terminal and a second input The terminal is connected to the first output terminal and the second output terminal of the second differential amplifier.